1. Field of the Invention
The invention relates to a sheet jamming-proof mechanism in a paper-feeding system, and more particularly, to a sheet jamming-proof mechanism for an image scanner.
2. Description of the Related Art
The paper-feeding system has been widely used in various machines such as scanner, photocopier, printer, and fax machine. Sheet jamming can be caused by aging of equipment or improper operation of a paper-feeding system. However, neither a sheet jamming-proof mechanism nor a fault-eliminating apparatus designed for helping users when sheet jamming occurred is seen in the typical paper-feeding systems. As sheet jamming occurs, the user practiced in the machine usually opens the cover of machine and pulls the jammed paper out, which causes a relatively serious attrition to the machine. For those who are not familiar to the operation of the machine, it is even impossible to take out the jammed paper without asking somebody else for help.
To solve the aforesaid problems, in Taiwanese Patent Application Ser. No. 85207086 (Patent Publication No. 291219) is disclosed a "scanning device having drawer cassette", by which jammed paper can be quickly eliminated by pulling the drawer cassette out when sheet jamming happens. Referring to FIG. 1A and 1B, there are shown the exploded perspective views of this scanning device which includes: a housing 2, a motor and reducing gear train I received within the housing 2, a drawer cassette 3, and a reflecting mirror 4. In the front panel of housing 2 are provided with a drawer cassette eject key 5, a document backward key 6, a document forward key 7, and a LED indicator 8. The drawer cassette 3, installed on slide guide 10 in housing 2 and being able to be drawn out from the housing, consists: a document inlet 31, a timing belt 32, a gear 33, a drawer cassette side flange 34, a document exit cover 35, a drawer cassette anchoring hole 36, a roller suite 37, a scanning window 38, a connecting rod 39 for anchoring drawer cassette, a pushing rod 310, a guiding groove 311, and a stopping spring 312.
When a document is jammed within the scanning passage, the user may press eject key 5 to slightly eject drawer cassette 3 by the tension of spring 312, glide the drawer cassette 3 out from slide guide 10, open document exit cover 35, and then take the jammed document out easily.
Also disclosed in Taiwanese Patent Application Ser. No. 84213349 (Patent Publication No. 282196) is a "Drawer type scanner structure integrated in a computer mainframe". The scanner provides a similar function for solving the sheet jamming problem. FIG. 2A and 2B show the exploded perspective views of the related scanner, wherein FIG. 2A shows the spatial positioning structure 100 of the scanner including: a main case 46, a bottom 41, a scanner case 42, an elastic locking member 43, a spring 44, a top cover 45, a first mounting seat 47, a second mounting seat 48, a locking portion 49, a lifting part 410, a roller 411, a rib 412, a restricting groove 413, a stopping portion 414, a panel 424, a feeding roller 421 which is provided within the scanner case 42, and a rail 415 provided on the inner surface of main case, each rail 415 consists a groove 416, while top cover 45 has two openings 423.
When sheet jamming occurs, the user first pushes scanner case 42 to move it toward locking member 43, then locking portion 49 is released from locking member 43 by the attribute of locking member 43 and scanner case 42 is protruded to expose outside the surface of the mainframe case (not shown). Thereby the user can raise the lifting part 410 of top cover 45 to remove the jammed document.
As described above, the sheet jamming problem can be solved by means of the aforesaid prior art. However, if we can detect and eliminate the sheet jamming at the very beginning when the document deviates from the predetermined direction, then the attrition to the machine can be reduced and the structure of the machine can be greatly simplified.
Therefore, an object of the invention is to provide a simply constructed sheet jamming-proof mechanism for paper-feeding system which can be applied to all machinery having paper-feeding system without limiting to a scanning apparatus.